The present invention relates to an apparatus for determining the carbon contents of molten metal and simultaneously accomplishing an effective sampling of molten metal and a measurement of a molten metal bath temperature.
There have been invented and used a variety of carbon determinators which may be directly placed in a molten metal bath for quick determination of the carbon contents thereof. An entry port of the carbon determinator is, in common case, provided in the upper portion of the container side-wall. A thermocouple measuring phase change temperature of the molten metal is set in the upper portion or the lower portion of the container, and consists of platinum platinum-rhodium wire insulated in a U-shaped quartz tube.
In such a carbon determinator with the thermocouple protruded from the bottom of the container, when the molten metal is sampled by the carbon determinator a shrinkage cavity is occasionally left adjacent to the entry port of the container and the form of the thermocouple is left in the bottom of the sample. Therefore, the portion of the sample which may be used as a specimen for spectrographic analysis will be quite limited. In the worst case, the shrinkage cavity adjacent to the entry port will be communicated with the cavity formed by the air contained in the quartz tube of the thermocouple. As a result, a cavity is formed in the center part of the sample, so that a reliable specimen for spectrographic analysis is not available.
In the carbon determinator in which the thermocouple is protruded from the upper portion of the container, since the molten metal sampling chamber is provided in the lower part of the container, even if the shrink cavity is formed in the adjacent portion of the entry port, the molten metal taken in the bottom of the container is sufficiently used for the spectrographic analysis. But, since the thermocouple is placed adjacent to the entry port, there exists the defect that the thermocouple is bent by the force of molten metal flowing into the container. The carbon contents of the molten metal is measured by the phase change temperature, but the correct measurement of the carbon contents is executed only when the thermocouple is set in the center of the container. In case the thermocouple is bent, the carbon contents should not be measured correctly and whether the carbon contents measured by such a faulty carbon determinator is correct or not is ascertained only after the molten metal is analyzed by other means. Thus, the reliability of the carbon determination performed by such means will not be accountable for the precise quality control in the metal industry.